EP0793124B1 - Ein durch Einschreiben eines Bragg-Gitters in eine optische Faser hergestelltes Filter - Google Patents

Ein durch Einschreiben eines Bragg-Gitters in eine optische Faser hergestelltes Filter Download PDF

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Publication number
EP0793124B1
EP0793124B1 EP97400405A EP97400405A EP0793124B1 EP 0793124 B1 EP0793124 B1 EP 0793124B1 EP 97400405 A EP97400405 A EP 97400405A EP 97400405 A EP97400405 A EP 97400405A EP 0793124 B1 EP0793124 B1 EP 0793124B1
Authority
EP
European Patent Office
Prior art keywords
fiber
bragg grating
mode
optical
pitch
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Expired - Lifetime
Application number
EP97400405A
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English (en)
French (fr)
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EP0793124A1 (de
Inventor
Fatima Bakhti
Pierre Sansonetti
Isabelle Riant
François GONTHIER
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Oclaro North America Inc
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Oclaro North America Inc
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    • G—PHYSICS
    • G02—OPTICS
    • G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
    • G02B6/00—Light guides; Structural details of arrangements comprising light guides and other optical elements, e.g. couplings
    • G02B6/02—Optical fibres with cladding with or without a coating
    • G02B6/02057—Optical fibres with cladding with or without a coating comprising gratings
    • G02B6/02076—Refractive index modulation gratings, e.g. Bragg gratings
    • G02B6/0208—Refractive index modulation gratings, e.g. Bragg gratings characterised by their structure, wavelength response
    • G02B6/021—Refractive index modulation gratings, e.g. Bragg gratings characterised by their structure, wavelength response characterised by the core or cladding or coating, e.g. materials, radial refractive index profiles, cladding shape
    • G—PHYSICS
    • G02—OPTICS
    • G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
    • G02B6/00—Light guides; Structural details of arrangements comprising light guides and other optical elements, e.g. couplings
    • G02B6/02—Optical fibres with cladding with or without a coating
    • G02B6/02057—Optical fibres with cladding with or without a coating comprising gratings
    • G02B6/02076—Refractive index modulation gratings, e.g. Bragg gratings
    • G02B6/0208—Refractive index modulation gratings, e.g. Bragg gratings characterised by their structure, wavelength response
    • G02B6/02085—Refractive index modulation gratings, e.g. Bragg gratings characterised by their structure, wavelength response characterised by the grating profile, e.g. chirped, apodised, tilted, helical
    • G02B6/02095—Long period gratings, i.e. transmission gratings coupling light between core and cladding modes
    • G—PHYSICS
    • G02—OPTICS
    • G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
    • G02B6/00—Light guides; Structural details of arrangements comprising light guides and other optical elements, e.g. couplings
    • G02B6/10—Light guides; Structural details of arrangements comprising light guides and other optical elements, e.g. couplings of the optical waveguide type
    • G02B6/14—Mode converters
    • G—PHYSICS
    • G02—OPTICS
    • G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
    • G02B6/00—Light guides; Structural details of arrangements comprising light guides and other optical elements, e.g. couplings
    • G02B6/02—Optical fibres with cladding with or without a coating
    • G02B6/02047—Dual mode fibre

Definitions

  • the present invention relates generally to optical filters. More particularly, the invention relates to rejector and bandpass filters.
  • At least one photorefractive network, or network of Bragg, inscribed in an optical fiber uses the principle fundamental variation of the refractive index of the heart fiber, typically doped with germanium, by illumination at the UV. as described in US patent US-A-4,474 427.
  • a holography technique recalled in document US-A-4,725 110, or a point-by-point technique described in US-A-5 104 209, or a mask technique phase disclosed in US-A-5,367,588.
  • the main drawback of the described embodiment in this document is an imperfect coupling between modes of heart and sheath, which results from the small cross section of the heart fiber, Bragg wavelength sensitivity a priori five times higher than the sensitivity in a conventional short pitch Bragg grating, and the presence of several sheath modes.
  • the invention aims to remedy this drawback by providing an optical rejector filter formed by writing at least one long-pitch Bragg grating in an optical fiber, which is characterized in that the optical fiber, initially monomode, is tapered to define two substantially adiabatic transition zones delimiting an intermediate zone in which two modes can be guided, and in that said long-pitch Bragg grating is inscribed in said intermediate zone to produce a codirectional coupling between the two guided modes, of core and of cladding, at a wavelength which is a function of the pitch of said grating.
  • the invention also provides an optical bandpass filter. which differs from the rejector filter presented above in that it further comprises a second network of Bragg which is registered in that of said two zones of transition which is arranged at the reception entrance of a optical signal.
  • a tapered optical fiber carried by a z-oriented axis, for the production of filters according to the invention.
  • a fiber tapered optics is for example obtained by fusion and stretching of a unimodal optical fiber comprising a core 10 and a sheath 11 as described in the article entitled “Spectral filtering by unimodal tapered fibers - Application to WDM couplers ", by Jacques Bures et al. published in "OPTO'89, pp 75-78, Esi-Publi".
  • the transition zone Z1 is such that the diameter d of the fiber varies in decreasing order as a function of z from a diameter equal to the diameter d2 fiber up to a diameter equal to a minimum diameter d1.
  • the intermediate zone Z2 has over its entire length the minimum diameter d1.
  • the second transition zone Z3 is such that the fiber diameter varies by increasing in function of z from a diameter equal to the diameter minimum d1 up to the diameter d2 of the fiber.
  • the diameter of the core 10 of the fiber varies accordingly to possess a almost zero diameter in the intermediate zone Z2.
  • the slope of variation of the diameter d of the fiber as a function of z in the transition zones Z1 and Z3 is sufficient low to meet the criterion of adiabaticity, such as this is explained in the aforementioned article as well as in the document entitled "Tapered single-mode fibers and devices" by J.D LOVE et al. published in "IEE Proceedings-J, vol.138, N ° 5, October 1991 ".
  • a region is said to be adiabatic if the couplings between modes, due to the slope of the fiber, are weak or negligible.
  • a mode of heart, noted LP01 propagating in the continuous single-mode fiber of propagate in the form of an LP01 mode after switching to through zone Z1, without giving birth to any other mode.
  • a rejector filter to inscribe a Bragg grating with a long pitch 2 in the intermediate zone Z2 of the tapered fiber. It is assumed that this intermediate zone Z2 is capable of being the subject of a Bragg grating inscription, by providing for example a Germanium doping of the sheath 11.
  • the Bragg grating with long pitch is of the type described in the aforementioned article "Long period fiber gratings as band-rejection filters" by AM VENGSARKAR et al, published in OFC'95, PD4, (1995).
  • the optical phenomena applying to the embodiment described here are as follows.
  • FIG. 1 it is assumed that the incoming optical signal S10 propagates in the direction of increasing z in the single-mode fiber.
  • the tapered part Z1-Z2-Z3 of the fiber receives this incoming optical signal S10 propagating in LP01 mode, or core mode, and having a spatial distribution of the Gaussian type.
  • the optical signal S10 of mode LP01 crosses the adiabatic transition zone Z1 without giving rise to other modes. It therefore continues to propagate in the intermediate zone Z2 according to this mode LP01, not in the core 10 of the fiber, but in its sheath 11, the core being substantially nonexistent in the intermediate zone Z2.
  • the long pitch Bragg grating 2 introduces a codirectional coupling between the LP01 mode and an LP02 mode guided in the zone Z2, at a wavelength which is a function of the pitch of the grating 2.
  • the intermediate zone Z2 having a larger diameter than the diameter of the core 10, this results in a more efficient coupling than that obtained in a fiber core when the long-pitch network is inscribed in a non-tapered optical fiber.
  • This coupling gives rise to a signal S11 of mode LP01, directly coming from the signal S10, and to a signal S12 of mode LP02 which conveys the power of the incident optical signal at the coupling wavelengths.
  • the signal S12 of mode LP02 will attenuate as the distance traveled by leakage at the sheath-coating interface in the part of single mode fiber. Only the signal S11 of LP01 mode propagates durably in the core of the fiber, presenting a rejection band centered on the coupling wavelength ⁇ C which is a function of the pitch of the network 2, as shown in the figure. 3.
  • the values of the constants ⁇ 1 and ⁇ 2 being relatively close, a relatively long step ⁇ is obtained, of the order of several hundreds of ⁇ m for wavelengths of the order of ⁇ m.
  • a bandpass filter according to the invention differs from the rejector filter presented in FIG. 1 in that it further comprises a second Bragg grating 3 inscribed in the transition zone Z1 which is disposed at the input for receiving the optical signal S20.
  • the additional Bragg grating 3 is inscribed in the transition zone Z1 of the fiber which is arranged at the optical signal reception input.
  • the effective index n eff of the fiber in this zone Z1 decreases as a function of z.
  • the inscription of the network in such a zone Z1 therefore entails a coupling between modes LP01 and LP02 over a large bandwidth.
  • an incoming optical signal S20 of mode LP01 couples with an optical signal S21 of mode LP02 substantially for the entire bandwidth of the incoming optical signal. Since the coupling occurs over a very wide band, it can be estimated that only the signal S21 of mode LP02 is delivered at the output of the network 3.
  • the long-pitch Bragg grating 2 receives signal S21 of mode LP02 and introduces a coupling codirectional between this LP02 mode and an LP01 mode, at one wavelength which is a function of the grid pitch 2.
  • This coupling gives rise to a signal S23 of LP02 mode, originating directly from signal S21, and to a signal S22 of LP01 mode which carries the power of the incoming optical signal S20 aux coupling wavelengths.
  • the signal S23 of mode LP02 fades as the distance traveled by leak at the sheath-coating interface, in the part single-mode fiber.

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  • Physics & Mathematics (AREA)
  • General Physics & Mathematics (AREA)
  • Optics & Photonics (AREA)
  • Light Guides In General And Applications Therefor (AREA)
  • Diffracting Gratings Or Hologram Optical Elements (AREA)
  • Optical Fibers, Optical Fiber Cores, And Optical Fiber Bundles (AREA)
  • Optical Filters (AREA)

Claims (2)

  1. Optisches Filter, das durch Einschreiben mindestens eines Bragg-Gitters mit langer Periode (2) in eine optische Faser gebildet ist, dadurch gekennzeichnet, daß
    die optische Faser verjüngt ist, um zwei im wesentlichen adiabatische Übergangszonen (Z1, Z3) zu bestimmen, welche eine Zwischenzone (Z2) begrenzen, und
    das Bragg-Gitter mit langer Periode (2) in die Zwischenzone (Z2) eingeschrieben ist, um eine kodirektionale Kopplung zwischen zwei geführten Moden (LPO1, LPO2) in der Zwischenzone (Z2) bei einer Wellenlänge zu bilden, die eine Funktion der Periode des Gitters (2) ist.
  2. Optisches Filter nach Anspruch 1, gekennzeichnet durch ein zweites Bragg-Gitter (3), das in diejenige (Z1) der zwei Übergangszonen (Z1, Z3) eingeschrieben ist, die am Aufnahmeeingang eines optischen Signals angeordnet ist.
EP97400405A 1996-03-01 1997-02-24 Ein durch Einschreiben eines Bragg-Gitters in eine optische Faser hergestelltes Filter Expired - Lifetime EP0793124B1 (de)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
FR9602620 1996-03-01
FR9602620A FR2745641B1 (fr) 1996-03-01 1996-03-01 Filtre obtenu par inscription d'un reseau de bragg dans une fibre optique

Publications (2)

Publication Number Publication Date
EP0793124A1 EP0793124A1 (de) 1997-09-03
EP0793124B1 true EP0793124B1 (de) 2004-12-01

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EP97400405A Expired - Lifetime EP0793124B1 (de) 1996-03-01 1997-02-24 Ein durch Einschreiben eines Bragg-Gitters in eine optische Faser hergestelltes Filter

Country Status (7)

Country Link
US (1) US5818987A (de)
EP (1) EP0793124B1 (de)
JP (1) JPH09329719A (de)
AU (1) AU707442B2 (de)
CA (1) CA2198768A1 (de)
DE (1) DE69731784T2 (de)
FR (1) FR2745641B1 (de)

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US6169830B1 (en) * 1996-08-26 2001-01-02 Arroyo Optics, Inc. Methods of fabricating grating assisted coupler devices
US6275627B1 (en) * 1998-09-25 2001-08-14 Corning Incorporated Optical fiber having an expanded mode field diameter and method of expanding the mode field diameter of an optical fiber
US6445851B1 (en) * 1998-12-15 2002-09-03 Arroyo Optics Inc. Tapered fiber gratings and applications
CA2258140C (en) * 1999-01-06 2003-02-18 Itf Optical Technologies Inc.-Technologies Optiques Itf Inc. Optical fiber filters and method of making the same
FR2788859B1 (fr) * 1999-01-25 2002-07-19 Cit Alcatel Fibre optique photosensible pour filtre a reseau de bragg, methode de fabrication de ladite fibre, et compensateur de dispersion chromatique et de pente de dispersion chromatique comprenant une telle fibre
GB2346965B (en) * 1999-02-18 2002-01-16 Oxford Fiber Optic Tools Ltd Fibre optic grating sensor
DE19911182C2 (de) 1999-03-12 2001-05-10 Profile Optische Systeme Gmbh Faser-Transmissionsbauelement zur Erzeugung chromatischer Dispersion
US6347171B1 (en) 1999-03-31 2002-02-12 Matsushita Electric Industrial Co., Ltd. Method and apparatus for forming a diffraction grating
US6278817B1 (en) 1999-08-31 2001-08-21 Corning, Incorporated Asymmetric low dispersion bragg grating filter
US6321005B1 (en) * 2000-08-23 2001-11-20 The United States Of America As Represented By The National Security Agency Device for dispersion compensation using tapered single-mode optical fiber
US6816260B2 (en) * 2001-05-17 2004-11-09 Thorlabs Gmbh Fiber polarimeter, the use thereof, as well as polarimetric method
US7495765B2 (en) * 2001-05-17 2009-02-24 Thorlabs Gmbh Fiber polarimeter, the use thereof, as well as polarimetric method
US6845194B2 (en) * 2001-06-27 2005-01-18 Furukawa Electric North America Inc. Optical bandpass filter using long period gratings
US6832025B2 (en) * 2001-07-02 2004-12-14 Jds Uniphase Corporation Fiber bragg grating fabrication method
KR100492874B1 (ko) * 2002-10-16 2005-06-02 광주과학기술원 광섬유 코어모드 제거기 및 그 제조방법
KR100448106B1 (ko) * 2002-10-16 2004-09-08 광주과학기술원 할로우 광섬유를 이용한 코어모드 제거기
FR2856482B1 (fr) * 2003-06-20 2005-11-11 Cit Alcatel Filtre optique
EP2369378B1 (de) * 2006-07-25 2013-10-30 The Board Of Trustees Of The Leland Stanford Junior University Hohlkernglasfasern mit Tapern
JP5354605B2 (ja) * 2009-02-10 2013-11-27 国立大学法人北海道大学 テーパ光ファイバ
CN103439262A (zh) * 2013-07-16 2013-12-11 深圳大学 基于光纤倏逝场的挥发性有机物检测装置及其制造方法

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CA1149209A (en) * 1980-07-09 1983-07-05 Paolo G. Cielo Evanescent-wave fiber reflector
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Also Published As

Publication number Publication date
FR2745641B1 (fr) 1998-04-10
US5818987A (en) 1998-10-06
EP0793124A1 (de) 1997-09-03
AU707442B2 (en) 1999-07-08
AU1498797A (en) 1997-09-04
CA2198768A1 (fr) 1997-09-01
JPH09329719A (ja) 1997-12-22
DE69731784D1 (de) 2005-01-05
DE69731784T2 (de) 2005-03-31
FR2745641A1 (fr) 1997-09-05

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